World's 'oldest' spider may have arrived 80 mln yrs later than previously thought

Published: Tuesday, December 23, 2008, 13:36 [IST]

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London, Dec 23 (ANI): Scientists have found that the species once described as the world's oldest spider is a more primitive version of the web-spinning modern spider, which has led to the theory that the oldest spider may have arrived 80 million years later than previously thought.

According to a report by BBC News, scientists found that the parts of the Attercopus spider's described as spinnerets - the appendages that allow web-spinning - were not spinnerets after all.

That means that the oldest "true" spider may have arrived 80 million years later than previously thought.

Paul Selden of the University of Kansas and his colleagues first described Attercopus fossil remains in 1989.

Most of what the group initially found among fossil remains belonged to a group of extinct arachnids called trigonotarbids, but one bit seemed to have the modified hairs called spigots from which spider silk emerges, as well as the external, flexible appendages known as spinnerets that facilitate web-spinning.

That led the group to believe they were looking at the world's oldest known spider.

However, also present in the mix of material from the rock was a tail-like structure, which the researchers could not identify. The analysis stopped there until more material from the site was recovered and analyzed.

In the new study, the researchers found a piece of Attercopus abdomen, with a tail attached.

The existence of such a tail was also relevant to the more recently discovered Permarachne genus, whose tail was originally described as an "elongated spinneret".

The finding prompted the team to return to their original samples, which on further study showed that the spinnerets they had earlier identified were in fact rolled-up pieces of cuticle, the animals' external skeletal material.

According to the researchers, it seems that Attercopus is a missing link, capable of producing silk but not of weaving it.

"The thing that had been called the oldest known spider we have now shown is in fact more primitive than a true spider," Professor Selden told BBC News.

The oldest "true spider", like the ones seen today, dates from the late Carboniferous period that ended about 300 million years ago, though Professor Selden said that true spiders may have existed earlier but have not yet been discovered. (ANI)